[Bugfix] Allow vllm to still work if triton is not installed. (#6786)

Signed-off-by: Thomas Parnell <tpa@zurich.ibm.com>

vllm/triton_utils/__init__.py

@@ -1,6 +1,10 @@
-from vllm.triton_utils.custom_cache_manager import (
-    maybe_set_triton_cache_manager)
+from vllm.triton_utils.importing import HAS_TRITON
 
-__all__ = [
-    "maybe_set_triton_cache_manager",
-]
+__all__ = ["HAS_TRITON"]
+
+if HAS_TRITON:
+
+    from vllm.triton_utils.custom_cache_manager import (
+        maybe_set_triton_cache_manager)
+
+    __all__ += ["maybe_set_triton_cache_manager"]